Question: Christopher is 76 years old and Luis is 4 years old. How many years will it take until Christopher is only 5 times as old as Luis?
Answer: We can use the given information to write down an equation about how many years it will take. Let $y$ be the number of years that it will take. In $y$ years, Christopher will be $76 + y$ years old and Luis will be $4 + y$ years old. At that time, Christopher will be 5 times as old as Luis. Writing this information as an equation, we get: $76 + y = 5 (4 + y)$ Simplifying the right side of this equation, we get: $76 + y = 20 + 5 y$ Solving for $y$ , we get: $4 y = 56$ $y = 14$.